The present invention relates to methods and apparatuses for processing semiconductor substrates (e.g., wafers, flat panel displays, etc.). More particularly, the present invention relates to methods and apparatuses for supplying process gases to a substrate processing chamber configured for processing such substrates.
Substrate processing involves, among other process steps, the selective deposition and removal of materials from the substrate surface. Many deposition and etching processes employ process source gases to perform the aforementioned deposition and etching. Plasma-enhanced etching is an example substrate processing process that employs a plurality of process gases in one or more processing steps.
In the following disclosure, plasma-enhanced etching and plasma-enhanced etching chambers are employed to illustrate various concepts and implementation examples. It should be understood, however, that the concepts and embodiments discussed herein may apply to any processing system or technology that employs one or more process gases in the processing of substrates.
In a typical plasma processing chamber, a plurality of source gases may be made available to the chamber. The available source gases are provided to a gas delivery system associated with the plasma processing chamber. Depending on the recipe requirements, a subset of the available gases may be provided by the gas delivery system to the chamber during any given process step.
For example, a recipe may call for 20 sccm (standard cubic centimeter) of N2, 60 sccm of CHF3, and 30 sccm of Ar to be delivered to chamber during a given recipe step. To control (i.e., turning on/off and/or meter) the flow of the required gases, each feed line that carries a specific gas from a gas feed source to the chamber may be equipped with a mass flow controller (MFC).
Thus a chamber that has 16 possible process gases available to it may be equipped with a gas supply system that employs 16 MFCs, with each MFC turning on/off and metering one of the 16 available gases. The individual constituent gases that flow during a particular process step (such as the aforementioned N2, CHF3 and Ar) may be mixed in a mixing manifold prior to being delivered to the chamber.
FIG. 1 shows an example prior art gas supply arrangement 100 whereby 16 MFCs (102A-102P) are coupled to 16 gas supply lines (104A-104P respectively). Each MFC can control the flow of the process gas to which it is coupled. By turning on/off an MFC and/or using that MFC to meter the flow, a process gas may be excluded from a processing step or provided to the chamber at the flow rate specified by the process recipe.
Although this arrangement has proven useful in the past, improvements can be made. With reference to the previously mentioned example, the use of 16 MFCs to control the 16 supplied gases dictates that the gas supply system and the enclosure 110 therefor be of a certain size to physically accommodate at least the 16 MFCs. The use of 16 MFCs also dictates that the mixing manifold 112 be sufficiently long to couple to the outlets of the 16 MFCs.
Further, the 16 MFCs and the large mixing manifold increase the gas supply system footprint as well as give rise to a large gas supply enclosure interior volume. Since environmental remediation requirements often necessitate the scrubbing of any gaseous material that exists in or is exhausted from the interior volume of the gas supply system enclosure, the larger interior volume results in increased cost as a larger volume of gaseous material needs to be scrubbed.
Further, a larger gas supply system enclosure requires the gas supply system to be located further away (relative to a smaller gas supply system, for example) from the chamber. As a consequence, a longer chamber gas supply line connecting the mixing manifold to the chamber is often required.
Still further, certain recipes require the pulsing of the supplied gases. For example, a recipe may require alternately pulsing between gas mixture 1 and gas mixture 2. In a pulsing application, the larger mixing manifold and the longer chamber gas supply line increase the gas residence time, making fast switching from one gas mixture to another gas mixture impractical.
For at least these reasons, improved gas supply arrangements for substrate processing chambers and methods therefor are desired.